This a simulator written in Tcl to simulate a network node carrying GSM and GPRS traffics with QoS mechanisms. The payload type including circuit-switched voice, VoIP and web traffic, and the performance including packet drop, delay can be analyzed. The implemented QoS mechanism is DiffServ, with 4 RED queues for different services with different priorities.-This is a simulator written in Tcl to simulate a network node carrying GSM and GPRS traffics with QoS mechanisms. The payload type including circuit-switched voice, VoIP and web traffic, and the performance including packet drop, delay can be analyzed. The implemented QoS mechanism is DiffServ, with 4 RED queues for different services with different priorities.